1. Field of the Invention
The present invention relates to a technique for retrieving sound critical points, such as “bridge” portions of music from audio signals of the sound, and more particularly to a sound critical point retrieving apparatus, a sound reproducing apparatus and a sound signal editing apparatus using this sound critical points retrieving method.
2. Description of the Related Art
A user's manner of listening to sound using a CD player is cited for the purpose of description as an example of a conventional manner of listening to sound. In the case where a user listens to sound recorded on an audio CD, in general, the sound is sequentially reproduced starting from the beginning of the CD or the user designates the desired track number which is then reproduced. In the case where the user desires to listen to sound starting from a point within a track, such as when the lyrics begin, at the start of the second verse or at the start of the bridge portion, the user should use the fast forward or rewind functions of the CD player in order to shift starting point of reproduction to the desired position within the track.
Next, a trial listening system for electronic music distribution (EMD) is cited as an example for the purpose of description. There are many trial listening systems for EMD wherein a user can listen to a part of the sound (approximately 20 to 30 seconds) for trial as a sample of the song being sold. In many cases, such a sample for trial listening is retrieved as a part of sound that most directly expresses the sound features for sales promotion. Concretely, a sample for trial listening provides a part of sound, such as a starting part of the lyrics or a part of the bridge portion.
In the above described CD player, a user wishes to listen to the bridge portion alone of a particular track recorded on a CD, the user must first start reproduction of this track. Then, the user operates the fast forward function and rewind function while listening to the song or viewing the counter displayed on the CD player in order to shift the starting point of reproduction to the beginning of the bridge portion. Such a method is inconvenient for the user from operational point of view. In addition, in the case where the user wants to get an impression of the music on one CD or a plurality of CDs in a short time, the user must repeat such shifting operations. Such a digest reproduction increases much inconvenience of the user.
In the case where a sample for trial listening is selected in a trial listening system for EMD, the producer of the content or the manufacture of the trial listening system first listens to the entirety of the sound. Next, the producer or manufacturer finds the portion that most directly expresses the sound features by means of manual operation. Such operation of editing the content is inefficient for the producer and manufacturer. In addition, the cost of such operation represents a major portion of the costs of such trial listening system.
The above described problems are caused by the following facts. That is to say, the audio content recorded on an audio CD or the like, that is widely distributed includes only a small amount of external data. This external data is the amount of time of reproduction of the signal, the starting time of each track, the finishing time of each track, and the like. It does not include data concerning sound critical points in regard to the sound features content, such as the time when the lyrics start, the time when the bridge starts, or the like.